1. Field of Invention
The current invention relates to security tags and more particularly, discloses a method for applying a capacitor strap or chip strap to an antenna to form an EAS or RFID security tag.
2. Description of Related Art
Electronic article surveillance (EAS) security tags, typically comprise a resonant circuit that utilize at least one coil and at least one capacitor that operate to resonate when exposed to a predetermined electromagnetic field (e.g., 8.2 MHz) to which the EAS tag is exposed. By way of example only, the coil and the capacitor are etched on a substrate whereby a multi-turn conductive trace (thereby forming the coil) terminates in a conductive trace pad which forms one plate of the capacitor. On the opposite side of the substrate another conductive trace pad is etched to form the second capacitor plate, while an electrical connection is made through the substrate from this second plate to the other end of the coil on the first side of the substrate; the non-conductive substrate then acts as a dielectric between the two conductive trace pads to form the capacitor. Thus, a resonant circuit is formed. Various different resonant tag products are commercially available and described in issued patents, for example, U.S. Pat. Nos. 5,172,461; 5,108,822; 4,835,524; 4,658,264; and 4,567,473 all describe and disclose electrical surveillance tag structures. However, such products utilize, and indeed require, substrates which use patterned sides of conductive material on both face surfaces of the substrate for proper operation. Special conductive structures and manufacturing techniques must be utilized on both substrate faces for producing such resonant tag products. Currently available EAS tag structures have numerous drawbacks. For example, since special patterning and etching techniques must be utilized on both sides of the available tags to produce the proper circuit, per unit processing time and costs are increased. Furthermore, the complexity of the manufacturing machinery required for production is also increased. Oftentimes, complex photo-etching processes are used to form the circuit structures. As may be appreciated, two sided photo-etching is generally time consuming and requires precise alignment of the patterns on both sides. Additional material is also necessary to pattern both sides, thus increasing the per unit material costs. U.S. Pat. No. 5,781,110 (Habeger, et al.) discloses the application of a dielectric ink substance on top of a spiral inductive element to form a capacitive element.
With particular regard to radio frequency identification (RFID) tags, RFID tags include an integrated circuit (IC) coupled to a resonant circuit as mentioned previously or coupled to an antenna (e.g., a dipole) which emits an information signal in response to a predetermined electromagnetic field (e.g., 13.56 MHz). Recently, the attachment of the IC has been accomplished by electrically-coupling conductive flanges to respective IC contacts to form a “chip strap.” This chip strap is then electrically coupled to the resonant circuit or antenna. See for example U.S. Pat. Nos. 6,940,408 (Ferguson, et al.); 6,665,193 (Chung, et al.); 6,181,287 (Beigel); and 6,100,804 (Brady, et al.).
Furthermore, it has been determined that the formation of the capacitive element of the EAS circuit or of the RFID circuit is what substantively controls the tuning of the EAS resonant circuit, or the RFID circuit, to respond properly to the desired electromagnetic field. The assignee of the present application, namely, Checkpoint Systems, Inc. has filed on Oct. 25, 2005, U.S. Application Ser. No. 60/730,053 entitled “Capacitor Strap” which discloses a flexible capacitor strap that can be applied to an antenna circuit to form an EAS security tag.
However, there remains a need to apply a plurality of either chip straps or capacitor straps in large quantities and to do so efficiently. The method of the present invention provides a solution to this problem.
All references cited herein are incorporated herein by reference in their entireties.